i have an incase slider, and its pretty good, but depending on how specific you are about scratches, the slider does leave some marks where the rubber rails touch of the surface of the back of the phone.
I dont know about the other case as i have never owned one.
Personally, i use an invisible shield back and a power support anti-glare front.
the invisible shield is basically unscratchable, it is one of the toughest films i have ever seen. I recommend that.